No warnings when reading from a file only opened for appending.

[p5pRT]

Migrated from rt.perl.org#55420 (status was 'open')

Searchable as RT55420$

[p5pRT]

From @pjf

Created by @pjf

G'day p5p and readers of perlbugs,

Under all versions of Perl I have on my laptop (5.8.4, 5.8.8, 5.10.0, and
5.11.0) the following produces a warning​:

  open(FOO, '>', 'foo.txt');
  <FOO>;

However writing a file for appending doesn't​:

  open(FOO, '>>', 'foo.txt');
  <FOO>;

I thought this would be easy enough to fix​:

Inline Patch

diff --git a/pp_hot.c b/pp_hot.c
index 64b5fc5..bc0d5fe 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1586,7 +1586,8 @@ Perl_do_readline(pTHX)
         }
         else if (type == OP_GLOB)
             SP--;
-       else if (ckWARN(WARN_IO) && IoTYPE(io) == IoTYPE_WRONLY) {
+       else if (ckWARN(WARN_IO) && ( IoTYPE(io) == IoTYPE_WRONLY ||
+                                     IoTYPE(io) == IoTYPE_APPEND)) {
             report_evil_fh(PL_last_in_gv, io, OP_phoney_OUTPUT_ONLY);
         }
      }

However it looks like IoTYPE_APPEND also applies to files opened with mode '\+>>'\, and we certainly don't want to be warning there\.

Am I missing an IoTYPE that signifies a file is open for appending
only, or is the reason this bug is still around because we can't
easily spot the difference between the two?

Many thanks,

  Paul

--
Paul Fenwick <pjf@​perltraining.com.au> | http​://perltraining.com.au/
Director of Training | Ph​: +61 3 9354 6001
Perl Training Australia | Fax​: +61 3 9354 2681

Perl Info

Flags:
     category=core
     severity=low

Site configuration information for perl v5.8.8:

Configured by rurban at Sun Jul  8 19:08:44 GMT 2007.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
   Platform:
     osname=cygwin, osvers=1.5.24(0.15642), archname=cygwin-thread-multi-64int
     uname='cygwin_nt-5.1 reini 1.5.24(0.15642) 2007-01-31 10:57 i686 cygwin '
     config_args='-de -Dmksymlinks -Duse64bitint -Dusethreads -Uusemymalloc
-Doptimize=-O3 -Dman3ext=3pm -Dusesitecustomize -Dusedevel'
     hint=recommended, useposix=true, d_sigaction=define
     usethreads=define use5005threads=undef useithreads=define
usemultiplicity=define
     useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
     use64bitint=define use64bitall=undef uselongdouble=undef
     usemymalloc=n, bincompat5005=undef
   Compiler:
     cc='gcc', ccflags ='-DPERL_USE_SAFE_PUTENV -fno-strict-aliasing -pipe
-Wdeclaration-after-statement',
     optimize='-O3',
     cppflags='-DPERL_USE_SAFE_PUTENV -fno-strict-aliasing -pipe
-Wdeclaration-after-statement'
     ccversion='', gccversion='3.4.4 (cygming special, gdc 0.12, using dmd
0.125)', gccosandvers=''
     intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
     d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
     ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
     alignbytes=8, prototype=define
   Linker and Libraries:
     ld='ld2', ldflags =' -s -L/usr/local/lib'
     libpth=/usr/local/lib /usr/lib /lib
     libs=-lgdbm -ldb -ldl -lcrypt -lgdbm_compat
     perllibs=-ldl -lcrypt -lgdbm_compat
     libc=/usr/lib/libc.a, so=dll, useshrplib=true, libperl=libperl.a
     gnulibc_version=''
   Dynamic Linking:
     dlsrc=dl_dlopen.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' -s'
     cccdlflags=' ', lddlflags=' -s -L/usr/local/lib'

Locally applied patches:
     CYG01 - hints.cygwin.sh ldflags -s
     CYG02 - lib-ExtUtils-Embed insensitive against leading \\s
     CYG03 - lib-Test-Harness-Straps $ENV{PERL5LIB} = ''
     CYG04 - major.version.cygwin.sh cygperl-5_8.dll and not cygperl-5_8_x.dll
     CYG05 - add Win32CORE to core
     CYG07 - File-Spec-Cygwin-TMPDIR.patch
     Bug#38628 - allow legacy Cwd->cwd()
     Bug#40103 - File-Spec-case_tolerant.patch from 5.9.5


@INC for perl v5.8.8:
     /usr/lib/perl5/5.8/cygwin
     /usr/lib/perl5/5.8
     /usr/lib/perl5/site_perl/5.8/cygwin
     /usr/lib/perl5/site_perl/5.8
     /usr/lib/perl5/site_perl/5.8
     /usr/lib/perl5/vendor_perl/5.8/cygwin
     /usr/lib/perl5/vendor_perl/5.8
     /usr/lib/perl5/vendor_perl/5.8
     .


Environment for perl v5.8.8:
     HOME=/home/pjf
     LANG (unset)
     LANGUAGE (unset)
     LD_LIBRARY_PATH (unset)
     LOGDIR (unset)

PATH=/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/cygdrive/c/PROGRA~1/PerlEdit:/cygdrive/c/Perl/site/bin:/cygdrive/c/Perl/bin:/cygdrive/c/Perl/bin/:/cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:/cygdrive/c/WINDOWS/System32/Wbem:/cygdrive/c/Program
Files/VDMSound/:/cygdrive/c/Program Files/Common
Files/GTK/2.0/bin:/cygdrive/c/MinGW/bin:/cygdrive/c/Program
Files/gs/gs8.54/bin:/cygdrive/c/Program
Files/QuickTime/QTSystem/:/usr/local/bin/netpbm
     PERL_BADLANG (unset)
     SHELL (unset)

[p5pRT]

From @rgs

2008/6/7 via RT Paul Fenwick <perlbug-followup@​perl.org>​:

Under all versions of Perl I have on my laptop (5.8.4, 5.8.8, 5.10.0, and
5.11.0) the following produces a warning​:

   open\(FOO\, '>'\, 'foo\.txt'\);
   \<FOO>;

However writing a file for appending doesn't​:

   open\(FOO\, '>>'\, 'foo\.txt'\);
   \<FOO>;

I thought this would be easy enough to fix​:

diff --git a/pp_hot.c b/pp_hot.c
index 64b5fc5..bc0d5fe 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@​@​ -1586,7 +1586,8 @​@​ Perl_do_readline(pTHX)
}
else if (type == OP_GLOB)
SP--;
- else if (ckWARN(WARN_IO) && IoTYPE(io) == IoTYPE_WRONLY) {
+ else if (ckWARN(WARN_IO) && ( IoTYPE(io) == IoTYPE_WRONLY ||
+ IoTYPE(io) == IoTYPE_APPEND)) {
report_evil_fh(PL_last_in_gv, io, OP_phoney_OUTPUT_ONLY);
}
}

However it looks like IoTYPE_APPEND also applies to files opened with mode
'+>>', and we certainly don't want to be warning there.

Am I missing an IoTYPE that signifies a file is open for appending
only, or is the reason this bug is still around because we can't
easily spot the difference between the two?

I think we could add a new IoTYPE.

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From zefram@fysh.org

Appending is not the only case where there is insufficient information
in IoTYPE. When a file handle is opened on a command pipe, it gets IoTYPE
'|' regardless of the direction of the pipe, so there's no warning for
reading from a write-only pipe​:

$ perl -lwe 'open(FOO, "|true") or die $!; $a = <FOO>; print "OK"'
OK

We should probably be looking a layer down, asking perlio about the
file handle. Since perlio is now mandatory, it can probably replace
most uses of IoTYPE.

-zefram